UFO experts say more should be done to uncover the truth about near misses in the skies after an investigation has revealed dozens of reported close calls between aircraft and mystery objects.

There were five reported incidents in UK airspace in April this year alone – where passenger plane pilots confirmed sighting an unknown object from the cockpit – two of which were judged to have involved a definite risk of collision.

Incidents have also been reported at Manchester and Liverpool Airport.

Real life X-Files investigator Nick Pope has described the findings by Newsquest’s Data Investigations Unit as “fascinating and disturbing” and he said the reports made to the UK Airprox Board raise “important defence, national security and air safety issues”.

Since May 2017, the Board which aims to enhance aircraft safety has reviewed 36 unknown object reports detailing airborne near misses across the country - and nearly a quarter were in the most serious risk category.

Author and journalist Mr Pope, who investigated UFO sightings for the Ministry of Defence in the 1990s, said: “It's clear that pilots and air traffic services personnel are witnessing many near misses in UK airspace.

“The suspension of flying at Gatwick Airport earlier this year leads the media and the public to assume such occurrences involve drones, but applying the UK Airprox Board's own guidelines, many of the reports being attributed to drone activity should more properly be characterized as 'unknown objects'.

“Pilots frequently see things in the skies that they can't identify. The UK Airprox Board has a significant number of such accounts and there are numerous reports in the MoD's UFO files.

“In most cases, sightings turn out to be birds, weather balloons, plastic bags or bin liners, or Chinese lanterns, while some are indeed attributable to drones.

“However, other cases remain unexplained even after thorough investigation, and this is of concern, especially if we're missing a trick by being too quick to blame drones.

“Pilots tend not to be comfortable reporting a 'UFO' sighting, because of the perceived stigma, so it's much easier to talk about 'unusual aircraft', 'unconventional helicopters' or 'drones'."

In April the US Navy issued guidance to its pilots, advising them what to do if they encounter 'unidentified aerial phenomena' - UAP being the recognized military term for what the public term UFOs.

While the guidance itself remains classified and won't be made public, Mr Pope says it's an encouraging sign and he would like to see something similar in the UK.

He added: “The situation has been under-resourced since the 2009 termination of the MoD's UFO program, and while I'm aware that the MoD continues to study such matters - being careful to avoid using the term 'UFO' - more should be done.

“Having investigated UFOs for the MoD back in the 1990s, I can confirm that whatever the true nature of the phenomenon, it raises important defence, national security and - as we see here - air safety issues.”

It is against the law to fly a drone above 400-ft or near to an airport boundary and if a drone recklessly or negligently endangers an aircraft it is a criminal offence and the operator could face up to five years in prison.

Interestingly - the majority of the most baffling reports reviewed by the UK Airprox Board, which is sponsored and funded by the CAA and the MAA (Military Aviation Authority), involved sightings of unknown objects at thousands of feet off the ground.

In eight out of nine cases, where the Board could not determine the nature of the object witnessed, reports detailed sightings at altitudes ranging from nearly 5,000-ft to 16,000-ft.

Drone pilot Jason Goodlad, who runs Hawk-Eye Vision Ltd in Stourbridge, West Midlands, said it would be a “struggle to get a drone up to 6,000 to 7,000-ft as the battery would die” and he added: “At a really high altitude it’s doubtful it would be a drone.”

Among the most puzzling incidents was a report in Manchester at 6.10pm on February 1, 2018, the pilot of an Airbus A321 was descending through 10,000-ft when he caught sight of a “greyish thin-profiled ‘something’ which passed very close at the same level down the left-hand side at great speed".

The report states: “His initial reaction was that he had seen an internal reflection in his glasses or the windshield, but it was immediately apparent the First Officer and another person on the flight deck had also seen it. None had a clear view because it was in the landing-light beam for a split second. The pilot noted that having seen balloons in flight before, this object did not fit that profile.”

It is not known which airline was involved but the A321 is among the planes operated by Thomas Cook Airlines and can carry up to 200 people.

Paranormal and UFO researcher David Taylor, from Halesowen, West Midlands, who is a member of the Association for the Scientific Study of Anomalous Phenomena (ASSAP), said: “The majority of all anomalous reports - I would say around 95 per cent - are explainable in rational terms, either with known phenomena such as misidentification, drones, birds, military tests etc and currently little understood phenomena such as ball lightning, earthquake lights etc.

“However, this isn't to say all reported anomalies are easily explainable, and we must resist the temptation to dismiss them all out of hand.”